______ from heart trouble for years, Professor White has to take medicine with him wherever he goes.
A. Suffered
B. To suffer
C. Suffering
D. Suffers
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______ his key, he couldn't enter the room.
A. Having been lost
B. Lose
C. He had lost
D. Having lost
______ in the hall for half an hour, the old man suddenly realized he had left the wallet in the car.
A. Having waited
B. Wait
C. To wait
D. Being waited
______ all the letters, I went outand had a drink.
A. Finish
B. Having finished
C. To finish
D. Finishing
While ______ a tunnel through the mountain, the workers discovered an underground lake.
A. built
B. to built
C. being built
D. building